Expanded Sodalite-Type Metal−Organic Frameworks: Increased Stability and H₂ Adsorption through Ligand-Directed Catenation

The torsion between the central benzene ring and the outer aromatic rings in 1,3,5-tri-p-(tetrazol-5-yl)phenylbenzene (H3TPB-3tz) and the absence of such strain in 2,4,6-tri-p-(tetrazol-5-yl)phenyl-s-triazine (H3TPT-3tz) are shown to allow the selective synthesis of noncatenated and catenated versions of expanded sodalite-type metal−organic frameworks. The reaction of H3TPB-3tz with CuCl2·2H2O affords the noncatenated compound Cu3[(Cu4Cl)3(TPB-3tz)8]2·11CuCl2·8H2O·120DMF (2), while the reaction of H3TPT-3tz with MnCl2·4H2O or CuCl2·2H2O generates the catenated compounds Mn3[(Mn4Cl)3(TPT-3tz)8]2·25H2O·15CH3OH·95DMF (3) and Cu3[(Cu4Cl)3(TPT-3tz)8]2·xsolvent (4). Significantly, catenation helps to stabilize the framework toward collapse upon desolvation, leading to an increase in the surface area from 1120 to 1580 m2/g and an increase in the hydrogen storage capacity from 2.8 to 3.7 excess wt % at 77 K for 2 and 3, respectively. The total hydrogen uptake in desolvated 3 reaches 4.5 wt % and 37 g/L at 80 bar and 77 K, demonstrating that control of catenation can be an important factor in the generation of hydrogen storage materials.